According to a general subject material etching method, a substrate having a resist film formed on a surface is etched using a resist film as a mask (for example, see Patent Literature 1). For example, in an etching method disclosed in Patent Literature 1, a mixed gas in which a carbon-based gas is added to an etching gas is excited into a plasma state to etch a sapphire substrate, and the flow rate of the carbon-based gas is adjusted to adjust a tapered shape of convex portions.